My cousin served in the army ________ when he was ________.
| A．in 1990's; in twenties |
| B．in the 1990's; in the twenties |
| C．in the 1990s; in his twenties |
| D．in 1990's; in his twenties |
He thinks _____ history about Chinese is very important.
| A．studied | B．studying | C．studies | D．study |
How many states _______ the United States? Fifty.
| A．turn up | B．make up | C．end up | D．give up |
My mother is strict both _____ me and ____ her work.
| A．with; with | B．with; in | C．in; in | D．in; with |
------ Do you know where Li Ming is working _____? ------ Maybe in Guangzhou, I think.
| A．at first | B．at least | C．at last | D．at present |
You should keep working hard ____ you have passed the exam.
| A．since | B．because | C．so | D．even though |